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Blessed is the weak

By Sheldon Glashow

FOUR fundamental forces. It is an old refrain in physics. Gravity and
electromagnetism, along with the “strong” and “weak” nuclear forces, seem to
account for all that happens in the world. Gravity holds the stars together and
keeps our feet on the ground. The electromagnetic force binds electrons into
atoms and drives the complex web of chemical reactions that make our bodies
work. And the strong force glues neutrons and protons together into atomic
nuclei, and stands behind the life-giving energy of the Sun. It’s a nice
picture, satisfying and complete, and with each year, physicists come a little
closer to wrapping it all up in one ultimate unified theory.

Wait a minute. What about the weak force? Stars, atoms and nuclei are held
together by the other three forces. But where does the weak force come in? Is it
really necessary? And would the world be any different without it?

It was 100 years ago when the French physicist Henri Becquerel stumbled over
the effects of the weak force when he discovered radioactivity. Since then the
weak force has dwelt in relative obscurity, overshadowed by its three more
forthcoming sisters. We physicists now have a detailed theory that explains it,
and we can calculate how it works. But that’s mathematics. What does the weak
force really do?

A century is a long time for something so fundamental to remain so
ill-understood. But it doesn’t have to stay that way. Although the weak
interaction only shows its face in the quantum world, it isn’t really obscure,
and it affects all of us profoundly. To get to grips …